Tightening management of bolts, screws, etc., has been commonly performed by managing torque when tightening. However, for preventing these from loosening, it is desired to directly measure tightening axial force rather than the tightening torque for management, and axial force sensors are therefore required.
Axial force sensors have other uses such as suspension test apparatuses and electric disk brakes. For example, Patent Literature 1 describes an axial force sensor to be used for an electric disk brake. This axial force sensor is configured with a pair of pressing plates and a plurality of crystal piezoelectric elements held sandwiched by the pair of pressing plates, and can, when a compressive force is applied to the pair of pressure plates, detect an axial force thereof by the crystal piezoelectric elements.
Also, Patent Literature 2 describes a suspension axial force measurement apparatus. For this axial force measurement apparatus, an axial force measuring section is provided over a suspension, and the suspension is supported by a mount via the axial force measuring section. As the axial force measuring section, a 6-component dynamometer is used, so that an axial force of the suspension can be measured as six forces components.